The great modern economist, the Scottish moral philosopher Adam Smith, also came from philosophy and primarily described the behaviors of people in their economic actions and considerations. The “invisible hand” of the market, although only appearing once in the nearly 1000-page work “The Wealth of Nations”, established his reputation as a market liberal. The classics of economic theory expanded his ideas: David Ricardo broadened the horizon in foreign trade theory with his principle of comparative cost advantages; Jean-Baptiste Say focused on market supply and claimed, “every supply creates its own demand”. Socialist thinkers like Karl Marx focused on the increasing class difference between rich and poor, between owners (“capitalists”) and poor wage earners (“proletarians”) and their work at the subsistence level. Marx called for a reform towards a solidarity community or even a revolution.